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John Dalton
John Dalton's is most famous for his Atomic Theory. It is the following.
1. All matter is made of atoms. Atoms are indivisible and indestructible.
2. All atoms of a given element are identical in mass and properties.
3. Compounds are formed by a combination of two or more different kinds of atoms.
4. A chemical reaction is a rearrangement of atoms. There were no neutrons, protons, or electrons. Site: pearsonsuccessnet.com
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Joseph John Thomson
JJ Thomson discovered the electron. He did this by putting 2 charged plates on either side of a beam of light inside of a glass tube. He noticed the beam bent toward the positive plate. He concluded that there must be negative particles in the beam. Using this he came up with the plum pudding model. Electrons (plums) are surrounded by protons (pudding) Thomson didn't have any protons in his model. Also, the electrons orbit the nucleus. Site: atomictimeline.net
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Robert Millikan
Robert Millikan's most notable contribution to the atomic model is finding the charge of an electron. He did this by dropping tiny electrically charged oil particles between 2 metal surfaces. The weight he found is still the accepted weight today. Site: https://en.wikipedia.org/wiki/Oil_drop_experiment
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Ernest Rutherford
Ernest Rutherford found that the nucleus of an atoms is a dense, positively charged ball located at the center of the atom. He did this by shooting alpha particles at gold foil. He realized that most of the particles bounced back towards the source, instead of all of the alpha particles going straight through. A flaw in his work is that he did not show any neutrons. Site: pearsonsuccessnet.com
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Neils Bohr
Neils Bohr discovered that electrons travel in separate orbits around the nucleus. Also, he discovered that the number of electrons in the outer orbit determines its properties. A flaw is that he had a planetary model, much like our solar system. Small, negatively charged electrons (planets) orbit a large, positively charged nucleus (sun). He didn't include the neutrons. Site: pearsonsuccessnet.com
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Erwin Schrodinger
Schrodinger came up with the electron cloud model. This model elaborates upon Bohr's. Unlike Bohr's, Schrodinger's model showed the likelihood an electron had of being at a certain place at a certain time. The electron cloud model is currently an accepted model of the atom. Site: https://www.msnucleus.org/membership/html/jh/physical/atomictheory/lesson1/atomic1g.html
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Werner Heisenberg
Werner Heisenberg's most notable contribution to the Atomic Model is his Uncertainty Principle. This states that it is impossible to know the exact position and velocity of an electron simultaneously. This theory applies today. Site: https://www.britannica.com/science/uncertainty-principle
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James Chadwick
James Chadwick discovered the neutron in 1932. He won the Nobel Prize in Physics for his discovery. Int 1930, it was found that Beryllium emitted radiation when bombarded by alpha particles. This radiation had no charge. However, the radiation did not discharge electroscopes. This evidence proved the existence of the neutron. This model doesn't include quarks, which is a flaw. Site: http://dev.physicslab.org/Document.aspx
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Lise Meitner
In 1938, Lise Meitner discovered nuclear fission. She did this by bombarding uranium with neutrons. Her model and thinking are thought to be correct right now. Site: https://www.aps.org/publications/apsnews/200712/physicshistory.cfm
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